Food influences body clock and may ease jet lag

Food could be a new weapon in shaking off the effects of jet lag after research in mice showed that the insulin released as a result of eating can be a key factor in restoring a disrupted body clock.

Miho Sato and her colleagues at The Research Institute for Time Studies at Yamaguchi University in Japan did experiments in mice and tissue cultures to show, for the first time, that increases in insulin affect circadian rhythms. These daily rhythms affect alertness, sleep patterns, and mediate many other physiological processes.

Your biological clock is regulated by two broad factors: first, the central rhythm is reset daily by light, as sensory input from the eyes is processed by a small part of the brain called the suprachiasmatic nucleus. The rise and fall of hormones linked to sleep, for example, match this rhythm. But circadian rhythms are also present in peripheral "clocks" in a wide range of cell types in the body. Some of these can be influenced by food.

Sato demonstrated the role of insulin by shifting the peripheral body clock in the livers of mice by feeding them only at night. They then split the mice into two groups, supressed insulin levels in one group, and returned all the mice to daytime feeding. Four days later, the livers of the non-supressed mice had readjusted to a normal daily rhythm, as revealed by the daily rise and fall of liver-gene expression. The livers of the insulin-suppressed mice had still not returned to normal.

Jet lag tip

If human body clocks are similar to mouse ones, Sato's study suggests that people suffering from jetlag could adjust their eating patterns to get their internal clocks back to normal more quickly. "During jet lag, our bodies on their own may adapt very slowly. But we can make use of the knowledge of our study. If you were flying from London to Japan, you'd have an eight-hour phase-advance. So from our study using mice, the correct time to eat more would be earlier in the day."

Biologist Urs Albrecht at the University of Fribourg in Switzerland welcomes the research. "In the orchestra of the human body – where every cell has a clock running – the conductor is the suprachiasmatic nucleus in your brain. But the environmental signal of food also has an impact on the circadian patterns scattered across the body. Somehow, no one had looked at it in this way before.

"We now have the detailed biological explanation for why our bad habits of sitting in front of the TV and eating something before we go to bed are pretty silly," Albrecht added. "Enjoy your restless sleep!"

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